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Editing: urlparse.py

"""Parse (absolute and relative) URLs.

urlparse module is based upon the following RFC specifications.

RFC 3986 (STD66): "Uniform Resource Identifiers" by T. Berners-Lee, R. Fielding
and L.  Masinter, January 2005.

RFC 2732 : "Format for Literal IPv6 Addresses in URL's by R.Hinden, B.Carpenter
and L.Masinter, December 1999.

RFC 2396:  "Uniform Resource Identifiers (URI)": Generic Syntax by T.
Berners-Lee, R. Fielding, and L. Masinter, August 1998.

RFC 2368: "The mailto URL scheme", by P.Hoffman , L Masinter, J. Zwinski, July 1998.

RFC 1808: "Relative Uniform Resource Locators", by R. Fielding, UC Irvine, June
1995.

RFC 1738: "Uniform Resource Locators (URL)" by T. Berners-Lee, L. Masinter, M.
McCahill, December 1994

RFC 3986 is considered the current standard and any future changes to
urlparse module should conform with it.  The urlparse module is
currently not entirely compliant with this RFC due to defacto
scenarios for parsing, and for backward compatibility purposes, some
parsing quirks from older RFCs are retained. The testcases in
test_urlparse.py provides a good indicator of parsing behavior.

The WHATWG URL Parser spec should also be considered.  We are not compliant with
it either due to existing user code API behavior expectations (Hyrum's Law).
It serves as a useful guide when making changes.

"""

import re
import os

__all__ = ["urlparse", "urlunparse", "urljoin", "urldefrag",
           "urlsplit", "urlunsplit", "parse_qs", "parse_qsl"]

# A classification of schemes ('' means apply by default)
uses_relative = ['ftp', 'http', 'gopher', 'nntp', 'imap',
                 'wais', 'file', 'https', 'shttp', 'mms',
                 'prospero', 'rtsp', 'rtspu', '', 'sftp',
                 'svn', 'svn+ssh']
uses_netloc = ['ftp', 'http', 'gopher', 'nntp', 'telnet',
               'imap', 'wais', 'file', 'mms', 'https', 'shttp',
               'snews', 'prospero', 'rtsp', 'rtspu', 'rsync', '',
               'svn', 'svn+ssh', 'sftp','nfs','git', 'git+ssh']
uses_params = ['ftp', 'hdl', 'prospero', 'http', 'imap',
               'https', 'shttp', 'rtsp', 'rtspu', 'sip', 'sips',
               'mms', '', 'sftp', 'tel']

# These are not actually used anymore, but should stay for backwards
# compatibility.  (They are undocumented, but have a public-looking name.)
non_hierarchical = ['gopher', 'hdl', 'mailto', 'news',
                    'telnet', 'wais', 'imap', 'snews', 'sip', 'sips']
uses_query = ['http', 'wais', 'imap', 'https', 'shttp', 'mms',
              'gopher', 'rtsp', 'rtspu', 'sip', 'sips', '']
uses_fragment = ['ftp', 'hdl', 'http', 'gopher', 'news',
                 'nntp', 'wais', 'https', 'shttp', 'snews',
                 'file', 'prospero', '']

# Characters valid in scheme names
scheme_chars = ('abcdefghijklmnopqrstuvwxyz'
                'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
                '0123456789'
                '+-.')

# Leading and trailing C0 control and space to be stripped per WHATWG spec.
# == "".join([chr(i) for i in range(0, 0x20 + 1)])
_WHATWG_C0_CONTROL_OR_SPACE = '\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f '

# Unsafe bytes to be removed per WHATWG spec
_UNSAFE_URL_BYTES_TO_REMOVE = ['\t', '\r', '\n']

MAX_CACHE_SIZE = 20
_parse_cache = {}

def clear_cache():
    """Clear the parse cache."""
    _parse_cache.clear()

class ResultMixin(object):
    """Shared methods for the parsed result objects."""

@property
    def username(self):
        netloc = self.netloc
        if "@" in netloc:
            userinfo = netloc.rsplit("@", 1)[0]
            if ":" in userinfo:
                userinfo = userinfo.split(":", 1)[0]
            return userinfo
        return None

@property
    def password(self):
        netloc = self.netloc
        if "@" in netloc:
            userinfo = netloc.rsplit("@", 1)[0]
            if ":" in userinfo:
                return userinfo.split(":", 1)[1]
        return None

@property
    def hostname(self):
        netloc = self.netloc.split('@')[-1]
        if '[' in netloc and ']' in netloc:
            return netloc.split(']')[0][1:].lower()
        elif ':' in netloc:
            return netloc.split(':')[0].lower()
        elif netloc == '':
            return None
        else:
            return netloc.lower()

@property
    def port(self):
        netloc = self.netloc.split('@')[-1].split(']')[-1]
        if ':' in netloc:
            port = netloc.split(':')[1]
            if port:
                port = int(port, 10)
                # verify legal port
                if (0 <= port <= 65535):
                    return port
        return None

from collections import namedtuple

class SplitResult(namedtuple('SplitResult', 'scheme netloc path query fragment'), ResultMixin):

__slots__ = ()

def geturl(self):
        return urlunsplit(self)

class ParseResult(namedtuple('ParseResult', 'scheme netloc path params query fragment'), ResultMixin):

__slots__ = ()

def geturl(self):
        return urlunparse(self)

def urlparse(url, scheme='', allow_fragments=True):
    """Parse a URL into 6 components:
    <scheme>://<netloc>/<path>;<params>?<query>#<fragment>
    Return a 6-tuple: (scheme, netloc, path, params, query, fragment).
    Note that we don't break the components up in smaller bits
    (e.g. netloc is a single string) and we don't expand % escapes."""
    tuple = urlsplit(url, scheme, allow_fragments)
    scheme, netloc, url, query, fragment = tuple
    if scheme in uses_params and ';' in url:
        url, params = _splitparams(url)
    else:
        params = ''
    return ParseResult(scheme, netloc, url, params, query, fragment)

def _splitparams(url):
    if '/'  in url:
        i = url.find(';', url.rfind('/'))
        if i < 0:
            return url, ''
    else:
        i = url.find(';')
    return url[:i], url[i+1:]

def _splitnetloc(url, start=0):
    delim = len(url)   # position of end of domain part of url, default is end
    for c in '/?#':    # look for delimiters; the order is NOT important
        wdelim = url.find(c, start)        # find first of this delim
        if wdelim >= 0:                    # if found
            delim = min(delim, wdelim)     # use earliest delim position
    return url[start:delim], url[delim:]   # return (domain, rest)

def _checknetloc(netloc):
    if not netloc or not isinstance(netloc, unicode):
        return
    # looking for characters like \u2100 that expand to 'a/c'
    # IDNA uses NFKC equivalence, so normalize for this check
    import unicodedata
    n = netloc.replace(u'@', u'') # ignore characters already included
    n = n.replace(u':', u'')      # but not the surrounding text
    n = n.replace(u'#', u'')
    n = n.replace(u'?', u'')
    netloc2 = unicodedata.normalize('NFKC', n)
    if n == netloc2:
        return
    for c in '/?#@:':
        if c in netloc2:
            raise ValueError("netloc %r contains invalid characters "
                             "under NFKC normalization"
                             % netloc)

def _remove_unsafe_bytes_from_url(url):
    for b in _UNSAFE_URL_BYTES_TO_REMOVE:
        url = url.replace(b, "")
    return url

def urlsplit(url, scheme='', allow_fragments=True):
    """Parse a URL into 5 components:
    <scheme>://<netloc>/<path>?<query>#<fragment>
    Return a 5-tuple: (scheme, netloc, path, query, fragment).
    Note that we don't break the components up in smaller bits
    (e.g. netloc is a single string) and we don't expand % escapes."""
    url = _remove_unsafe_bytes_from_url(url)
    scheme = _remove_unsafe_bytes_from_url(scheme)
    url = url.lstrip(_WHATWG_C0_CONTROL_OR_SPACE)
    scheme = scheme.strip(_WHATWG_C0_CONTROL_OR_SPACE)
    allow_fragments = bool(allow_fragments)
    key = url, scheme, allow_fragments, type(url), type(scheme)
    cached = _parse_cache.get(key, None)
    if cached:
        return cached
    if len(_parse_cache) >= MAX_CACHE_SIZE: # avoid runaway growth
        clear_cache()
    netloc = query = fragment = ''
    i = url.find(':')
    if i > 0:
        if url[:i] == 'http': # optimize the common case
            scheme = url[:i].lower()
            url = url[i+1:]
            if url[:2] == '//':
                netloc, url = _splitnetloc(url, 2)
                if (('[' in netloc and ']' not in netloc) or
                        (']' in netloc and '[' not in netloc)):
                    raise ValueError("Invalid IPv6 URL")
            if allow_fragments and '#' in url:
                url, fragment = url.split('#', 1)
            if '?' in url:
                url, query = url.split('?', 1)
            _checknetloc(netloc)
            v = SplitResult(scheme, netloc, url, query, fragment)
            _parse_cache[key] = v
            return v
        for c in url[:i]:
            if c not in scheme_chars:
                break
        else:
            # make sure "url" is not actually a port number (in which case
            # "scheme" is really part of the path)
            rest = url[i+1:]
            if not rest or any(c not in '0123456789' for c in rest):
                # not a port number
                scheme, url = url[:i].lower(), rest

if url[:2] == '//':
        netloc, url = _splitnetloc(url, 2)
        if (('[' in netloc and ']' not in netloc) or
                (']' in netloc and '[' not in netloc)):
            raise ValueError("Invalid IPv6 URL")
    if allow_fragments and '#' in url:
        url, fragment = url.split('#', 1)
    if '?' in url:
        url, query = url.split('?', 1)
    _checknetloc(netloc)
    v = SplitResult(scheme, netloc, url, query, fragment)
    _parse_cache[key] = v
    return v

def urlunparse(data):
    """Put a parsed URL back together again.  This may result in a
    slightly different, but equivalent URL, if the URL that was parsed
    originally had redundant delimiters, e.g. a ? with an empty query
    (the draft states that these are equivalent)."""
    scheme, netloc, url, params, query, fragment = data
    if params:
        url = "%s;%s" % (url, params)
    return urlunsplit((scheme, netloc, url, query, fragment))

def urlunsplit(data):
    """Combine the elements of a tuple as returned by urlsplit() into a
    complete URL as a string. The data argument can be any five-item iterable.
    This may result in a slightly different, but equivalent URL, if the URL that
    was parsed originally had unnecessary delimiters (for example, a ? with an
    empty query; the RFC states that these are equivalent)."""
    scheme, netloc, url, query, fragment = data
    if netloc or (scheme and scheme in uses_netloc and url[:2] != '//'):
        if url and url[:1] != '/': url = '/' + url
        url = '//' + (netloc or '') + url
    if scheme:
        url = scheme + ':' + url
    if query:
        url = url + '?' + query
    if fragment:
        url = url + '#' + fragment
    return url

def urljoin(base, url, allow_fragments=True):
    """Join a base URL and a possibly relative URL to form an absolute
    interpretation of the latter."""
    if not base:
        return url
    if not url:
        return base
    bscheme, bnetloc, bpath, bparams, bquery, bfragment = \
            urlparse(base, '', allow_fragments)
    scheme, netloc, path, params, query, fragment = \
            urlparse(url, bscheme, allow_fragments)
    if scheme != bscheme or scheme not in uses_relative:
        return url
    if scheme in uses_netloc:
        if netloc:
            return urlunparse((scheme, netloc, path,
                               params, query, fragment))
        netloc = bnetloc
    if path[:1] == '/':
        return urlunparse((scheme, netloc, path,
                           params, query, fragment))
    if not path and not params:
        path = bpath
        params = bparams
        if not query:
            query = bquery
        return urlunparse((scheme, netloc, path,
                           params, query, fragment))
    segments = bpath.split('/')[:-1] + path.split('/')
    # XXX The stuff below is bogus in various ways...
    if segments[-1] == '.':
        segments[-1] = ''
    while '.' in segments:
        segments.remove('.')
    while 1:
        i = 1
        n = len(segments) - 1
        while i < n:
            if (segments[i] == '..'
                and segments[i-1] not in ('', '..')):
                del segments[i-1:i+1]
                break
            i = i+1
        else:
            break
    if segments == ['', '..']:
        segments[-1] = ''
    elif len(segments) >= 2 and segments[-1] == '..':
        segments[-2:] = ['']
    return urlunparse((scheme, netloc, '/'.join(segments),
                       params, query, fragment))

def urldefrag(url):
    """Removes any existing fragment from URL.

Returns a tuple of the defragmented URL and the fragment.  If
    the URL contained no fragments, the second element is the
    empty string.
    """
    if '#' in url:
        s, n, p, a, q, frag = urlparse(url)
        defrag = urlunparse((s, n, p, a, q, ''))
        return defrag, frag
    else:
        return url, ''

try:
    unicode
except NameError:
    def _is_unicode(x):
        return 0
else:
    def _is_unicode(x):
        return isinstance(x, unicode)

# unquote method for parse_qs and parse_qsl
# Cannot use directly from urllib as it would create a circular reference
# because urllib uses urlparse methods (urljoin).  If you update this function,
# update it also in urllib.  This code duplication does not existin in Python3.

_hexdig = '0123456789ABCDEFabcdef'
_hextochr = dict((a+b, chr(int(a+b,16)))
                 for a in _hexdig for b in _hexdig)
_asciire = re.compile('([\x00-\x7f]+)')

def unquote(s):
    """unquote('abc%20def') -> 'abc def'."""
    if _is_unicode(s):
        if '%' not in s:
            return s
        bits = _asciire.split(s)
        res = [bits[0]]
        append = res.append
        for i in range(1, len(bits), 2):
            append(unquote(str(bits[i])).decode('latin1'))
            append(bits[i + 1])
        return ''.join(res)

bits = s.split('%')
    # fastpath
    if len(bits) == 1:
        return s
    res = [bits[0]]
    append = res.append
    for item in bits[1:]:
        try:
            append(_hextochr[item[:2]])
            append(item[2:])
        except KeyError:
            append('%')
            append(item)
    return ''.join(res)

def parse_qs(qs, keep_blank_values=0, strict_parsing=0, max_num_fields=None,
             separator=None):
    """Parse a query given as a string argument.

Arguments:

qs: percent-encoded query string to be parsed

keep_blank_values: flag indicating whether blank values in
            percent-encoded queries should be treated as blank strings.
            A true value indicates that blanks should be retained as
            blank strings.  The default false value indicates that
            blank values are to be ignored and treated as if they were
            not included.

strict_parsing: flag indicating what to do with parsing errors.
            If false (the default), errors are silently ignored.
            If true, errors raise a ValueError exception.

max_num_fields: int. If set, then throws a ValueError if there
            are more than n fields read by parse_qsl().
    """
    dict = {}
    for name, value in parse_qsl(qs, keep_blank_values, strict_parsing,
                                 max_num_fields, separator):
        if name in dict:
            dict[name].append(value)
        else:
            dict[name] = [value]
    return dict

class _QueryStringSeparatorWarning(RuntimeWarning):
    """Warning for using default `separator` in parse_qs or parse_qsl"""

# The default "separator" for parse_qsl can be specified in a config file.
# It's cached after first read.
_QS_SEPARATOR_CONFIG_FILENAME = '/etc/python/urllib.cfg'
_default_qs_separator = None

def parse_qsl(qs, keep_blank_values=0, strict_parsing=0, max_num_fields=None,
              separator=None):
    """Parse a query given as a string argument.

Arguments:

qs: percent-encoded query string to be parsed

keep_blank_values: flag indicating whether blank values in
        percent-encoded queries should be treated as blank strings.  A
        true value indicates that blanks should be retained as blank
        strings.  The default false value indicates that blank values
        are to be ignored and treated as if they were  not included.

strict_parsing: flag indicating what to do with parsing errors. If
        false (the default), errors are silently ignored. If true,
        errors raise a ValueError exception.

max_num_fields: int. If set, then throws a ValueError if there
        are more than n fields read by parse_qsl().

Returns a list, as G-d intended.
    """

if (not separator or (not isinstance(separator, (str, bytes)))) and separator is not None:
        raise ValueError("Separator must be of type string or bytes.")

# Used when both "&" and ";" act as separators. (Need a non-string value.)
    _legacy = object()

if separator is None:
        global _default_qs_separator
        separator = _default_qs_separator
        envvar_name = 'PYTHON_URLLIB_QS_SEPARATOR'
        if separator is None:
            # Set default separator from environment variable
            separator = os.environ.get(envvar_name)
            config_source = 'environment variable'
        if separator is None:
            # Set default separator from the configuration file
            try:
                file = open(_QS_SEPARATOR_CONFIG_FILENAME)
            except EnvironmentError:
                pass
            else:
                with file:
                    import ConfigParser
                    config = ConfigParser.ConfigParser()
                    config.readfp(file)
                    separator = config.get('parse_qs', envvar_name)
                    _default_qs_separator = separator
                config_source = _QS_SEPARATOR_CONFIG_FILENAME
        if separator is None:
            # The default is '&', but warn if not specified explicitly
            if ';' in qs:
                from warnings import warn
                warn("The default separator of urlparse.parse_qsl and "
                    + "parse_qs was changed to '&' to avoid a web cache "
                    + "poisoning issue (CVE-2021-23336). "
                    + "By default, semicolons no longer act as query field "
                    + "separators. "
                    + "See https://access.redhat.com/articles/5860431 for "
                    + "more details.",
                    _QueryStringSeparatorWarning, stacklevel=2)
            separator = '&'
        elif separator == 'legacy':
            separator = _legacy
        elif len(separator) != 1:
            raise ValueError(
                '{} (from {}) must contain '.format(envvar_name, config_source)
                + '1 character, or "legacy". See '
                + 'https://access.redhat.com/articles/5860431 for more details.'
            )

# If max_num_fields is defined then check that the number of fields
    # is less than max_num_fields. This prevents a memory exhaustion DOS
    # attack via post bodies with many fields.
    if max_num_fields is not None:
        if separator is _legacy:
            num_fields = 1 + qs.count('&') + qs.count(';')
        else:
            num_fields = 1 + qs.count(separator)
        if max_num_fields < num_fields:
            raise ValueError('Max number of fields exceeded')

if separator is _legacy:
        pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')]
    else:
        pairs = [s1 for s1 in qs.split(separator)]
    r = []
    for name_value in pairs:
        if not name_value and not strict_parsing:
            continue
        nv = name_value.split('=', 1)
        if len(nv) != 2:
            if strict_parsing:
                raise ValueError, "bad query field: %r" % (name_value,)
            # Handle case of a control-name with no equal sign
            if keep_blank_values:
                nv.append('')
            else:
                continue
        if len(nv[1]) or keep_blank_values:
            name = unquote(nv[0].replace('+', ' '))
            value = unquote(nv[1].replace('+', ' '))
            r.append((name, value))

return r

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